Functional Characterization of Ungulate Molars Using the Abrasion-Attrition Wear Gradient: A New Method for Reconstructing Paleodiets

Abstract

The analysis of fossil ungulate cheek teeth has long been one of the main sources of information about the terrestrial environments of the Cenozoic, but the methods used to extract this information have been either imprecise or prohibitively laborious. Here we present a method based on relative facet development that is quantitative, robust, and rapid. This method, which we term mesowear analysis, is based on the physical properties of ungulate foods as reflected in the relative amounts of attritive and abrasive wear that they cause on the dental enamel of the occlusal surfaces. Mesowear was recorded by examining the buccal apices of molar tooth cusps. Apices were characterized as sharp, rounded, or blunt, and the valleys between them either high or low. The method has been developed only for selenodont and trilophodont molars, but the principle is readily extendable to other crown types. Mesowear analysis is insensitive to wear stage as long as the very early and very late stages are excluded.Cluster analysis of the mesowear variables produces clusters reflecting four main groups from abrasion-dominated to attrition-dominated: grazers, graze-dominated mixed feeders, browse-dominated mixed feeders, and browsers. Most of the relatively few apparent anomalies are explained by more detailed dietary information. Mesowear analysis provides resolution within the main dietary classes and the clustering is virtually identical with and without the index of hypsodonty. Discriminant analysis using all mesowear variables and hypsodonty

Evidence of correlated evolution of hypsodonty and exceptional longevity in endemic insular mammals

“…When its wear signature is compared with the full dataset, the mean percentage correctly classified was only 53.7 per cent (29 of 54 species), with M. balearicus clearly not fitting the range of mixed feeders, but that of leaf browsers (figure 1b). Removing the 'MABRA' group (for 'minute abraded brachydonts'; see Fortelius & Solounias [39] for further explanation) notably contributed to increasing the correct classification rate for both the conservative (77.8%; figure 1c) and the radical (75.6%; figure 1d) dietary classifications. The most probable dietary assignment for M. balearicus corresponds to a browser according to both classifications.…”

Patterns of diet and body mass of large ungulates from the Pleistocene of Western Europe, and their relation to vegetation

“…Suidae was excluded because in the Middle and Late Pleistocene of Europe it is represented only by the wild boar (Sus scrofa), the fossils of which are rare, and the original mesowear scoring method of Fortelius and Solounias (2000) cannot be applied to bunodont teeth. Hippopotamus was excluded from the dietary analyses for the same reason, although it probably had a significant role in some interglacial mammal communities, such as the Ipswichian of Barrington, England (Gibbard and Stuart, 1975;Turner, 1975;Stuart, 1976;Stuart and Gibbard, 1986).…”

“…Highly abrasive diet typical for grazers causes low and blunt wear relief on the teeth. This method has been successfully applied to fossil ungulate teeth (e.g., Kaiser, 2004;Mihl-4 bachler and Solounias, 2006;Rivals et al, 2007;Croft and Weinstein, 2008;DeMiguel et al, 2008;Kahlke and Kaiser, 2011;Mihlbachler et al, 2011) and is grounded in studies of modern ungulates of known diet (e.g., Fortelius and Solounias, 2000;Clauss et al, 2007). Morphological adaptations improving wear resistance of herbivorous mammal teeth, such as increased molar crown height (hypsodonty), reflect the conditions under which they evolved and have been shown to be adaptive both to environmental factors (such as precipitation and erosion rates, which regulate the accumulation of mineral particles on plant material), as well as to dietary factors (abrasive food items, mainly grass).…”

The Morphophysiological Adaptations of Browsing and Grazing Mammals

“…Therefore, significant differences between GR and BR in enamel microwear or molar wear rates (Solounias et al 1994;Solounias and Semprebon 2002) are expected. As molar wear is a function of both attrition (tooth-to-tooth contact, which maintains sharp edges) and abrasion (tooth-to-food contact, which produces blunt edges), differences in the 'mesowear' pattern [the macroscopically evaluated shape and reliefs of the cusps of selected teeth first introduced by Fortelius and Solounias (2000)] between feeding types are also expected. Differences in mesowear patterns between upper and lower molars in different feeding types indicate different morphological adaptations (Franz-Oftedaal and Kaiser 2003;Kaiser and Fortelius 2003).…”